JERUSALEM — Sections of the main road running along the spine of the West Bank hills were closed off to Palestinian traffic yesterday, and Israeli officials portrayed this as the first step in a long-range plan to separate Israeli and Palestinian traffic completely and to sever contacts between the two populations.

The road closings came in the wake of drive-by shootings Sunday that left three Israelis dead and several wounded. Within hours of the incident, the government ordered the army to implement a contingency plan leading to separation of the Israeli and Palestinian populations.

The plan, which calls for the construction of bypasses and bridges, would create a Palestinian-only and Israeli-only road complex on the West Bank within two years. In addition, officials say, Palestinian workers’ entry into Israel would be halted within three years. Israel will encourage the international community to create economic opportunities for Palestinians inside the West Bank.

These steps, together with the barrier Israel is building along a line paralleling the border that existed before the 1967 Middle East war, are aimed at separating the two communities and reducing terror. They do not, however, represent an attempt to determine the future border between the two peoples, Israeli officials say. That matter still awaits political negotiations.

The Israeli military has debated whether separate road systems would reduce or enhance terror. Some officers say militants would feel free to fire on any vehicle on Israeli-only roads, but would not know whether an approaching vehicle on a mixed road was Israeli or Palestinian. However, it was decided that separated roads constituted a more secure system.

The Israeli decision is likely to draw opposition from Washington, which cautioned Jerusalem this week not to take steps that would make daily life more difficult for the Palestinians, such as limiting free movement among West Bank cities.

“We understand and support Israel’s right to defend itself. But at the same time, we urge them to consider the ramifications of their actions on the ultimate goal,” State Department spokesman Sean McCormack said.

He asked the Israeli government “to take steps to ease the daily plight of the Palestinian people.”

Palestinian Authority President Mahmoud Abbas is to meet with President Bush in Washington today. State Department spokesman Scott McClellan said the talks will focus on the upcoming parliamentary elections in the Palestinian Authority and on reform within the authority.